Detailed Description
In order to make the objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. Several embodiments of the invention are presented in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Like reference numerals refer to like elements throughout the specification.
The invention provides an optical imaging lens with large aperture, small distortion and thermal compensation performance, which comprises the following components in sequence from an object side to an imaging surface along an optical axis:
the lens comprises a first lens with negative focal power, a second lens and a third lens, wherein the object side surface of the first lens is a concave surface, and the image side surface of the first lens is a concave surface or a convex surface;
the second lens with positive focal power, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface or a plane;
a third lens having a positive optical power, the third lens having convex object and image side surfaces;
the fourth lens is provided with positive focal power, and the object side surface and the image side surface of the fourth lens are convex surfaces;
the fourth lens and the fifth lens form a cemented lens group;
the sixth lens with positive focal power is characterized in that the object side surface of the sixth lens is a convex surface, and the image side surface of the sixth lens is a concave surface or a convex surface;
a seventh lens having a negative optical power, the seventh lens having a concave object-side surface and a concave image-side surface;
and a stop located between the first lens and the third lens;
wherein the lenses before the stop form a first group, the lenses between the stop and the fourth lens form a second group, and the fourth lens, the fifth lens, the sixth lens and the seventh lens form a third group; the focal length f of the optical imaging lens is larger than 12 mm.
In some embodiments, the optical imaging lens satisfies the following conditional expression:
-100mm*℃<f3/(dn/dt)3+f4/(dn/dt)4<-30mm*℃;(1)
wherein f is3Denotes the focal length of the third lens, f4Denotes the focal length of the fourth lens, (dn/dt)3Represents a temperature refractive index coefficient of the third lens, (dn/dt)4Represents a temperature refractive index coefficient of the fourth lens.
The third lens and the fourth lens are both positive lenses and can effectively compensate rear focus offset and image resolution reduction caused by temperature change by controlling the temperature refractive index coefficients of the positive lenses, the rear focus offset of the lens is controlled within +/-2 mu m, the image resolution reduction is controlled within 8 percent, the temperature stability of the lens is effectively improved, and the lens keeps high image resolution in high and low temperature environments.
In some embodiments, the first group has a negative optical power, and the first group satisfies the following conditional expression:
-5.5mm/°<fQ1/ωST<0mm/°;(2)
wherein f isQ1Represents the focal length, ω, of the first groupSTThe line diagram of the marginal rays of the central field of view of the optical imaging lens, which represents the incident angle at the diaphragm, can be seen in fig. 19.
The condition formula (2) is satisfied, the aperture of the front end of the lens can be effectively reduced by controlling the incident angle of the marginal ray entering the diaphragm, the pupil radius can be enlarged, and the large aperture effect of the imaging system can be better realized.
In some embodiments, the second lens is an aspheric lens, and the second lens satisfies the conditional expression:
0<f2/R3<5;(3)
wherein f is2Denotes the focal length, R, of the second lens3The radius of curvature of the object side of the second lens is indicated.
Satisfy above-mentioned conditional expression (3), through the non-curved surface face type and the focus of reasonable control second lens, can effectively control the optical distortion of camera lens, reduce the deformation degree of the object of shooing, effectively improve the imaging quality.
In some embodiments, the first group satisfies the following conditional expression:
0<fQ1/R1<5;(4)
wherein f isQ1Denotes the focal length, R, of the first group1The radius of curvature of the object side of the first lens is indicated.
Satisfying the above conditional expression (4), the relative illumination of the lens can be effectively improved, if fQ1/R1If the value of (b) exceeds the upper limit, the processing difficulty of the lens is increased, and the yield is reduced; if fQ1/R1If the value of (b) exceeds the lower limit, the relative illumination of the imaging lens is too low, which may cause the edge brightness of the photographed picture to be reduced and even generate a dark angle.
In some embodiments, the second group has positive optical power, and the second group satisfies the following conditional expression:
0 mm/°<fQ2/ωex<4 mm/°;(5)
wherein f isQ2Denotes the focal length, ω, of the second groupexThe exit angle of marginal field rays representing the image side of the third lens.
The condition formula (5) is satisfied, the included angle between the emergent light of the second group and the optical axis of the system can be effectively reduced, so that the light enters the third group at a smaller angle, the tolerance sensitivity of the third group can be effectively reduced, the assembly yield of the lens is improved, and the cost is reduced.
In some embodiments, the optical imaging lens satisfies the following conditional expression:
0.3<f3/R6+f4/R7<1;(6)
wherein f is3Denotes the focal length of the third lens, f4Denotes the focal length, R, of the fourth lens6Represents a radius of curvature, R, of an image-side surface of the third lens7Representing said fourth lensRadius of curvature of the object side.
The condition formula (6) is satisfied, ghost images generated by the reflection light of the lens of the third group on the image side surface of the third lens can be effectively avoided, the generation of the ghost images on the imaging surface is reduced, and the imaging quality of the imaging lens is effectively improved.
In some embodiments, in order to effectively correct curvature of field of the imaging system, the optical imaging lens satisfies the following conditional expression:
-0.5<f6/R10-f7/R12<1;(7)
-2.5 mm<f6/f7*CT67<-0.5 mm;(8)
wherein f is6Denotes a focal length, f, of the sixth lens7Denotes a focal length, R, of the seventh lens10Represents a radius of curvature, R, of an object-side surface of the sixth lens12Represents a radius of curvature, CT, of an object-side surface of the seventh lens67An air space on the optical axis of the sixth lens and the seventh lens is indicated.
In some embodiments, the optical imaging lens satisfies the following conditional expression:
12mm<f<16mm;(9)
0.3<f/TTL<0.5;(10)
3mm2/°<IH/θ*f<4mm2/°;(11)
wherein f represents the focal length of the optical imaging lens, TTL represents the total optical length of the optical imaging lens, θ represents the half-field angle of the optical imaging lens, and IH represents the real image height of the optical imaging lens at the position corresponding to the half-field angle θ.
Satisfying the above conditional expressions (9) to (10), the imaging lens can be ensured to have a sufficiently large focal length, and the shooting distance of the imaging lens can be increased, so that the lens can shoot objects with longer distances; meanwhile, the condition formula (11) is also met, so that the imaging lens has a larger imaging surface under a smaller field angle, and further, a shot picture can contain more details, imaging is clearer, and the imaging quality of the imaging lens is effectively improved.
In some embodiments, the optical imaging lens satisfies the following conditional expression:
1<D1/DST<1.3;(12)
wherein D is1Representing the effective aperture of the first lens, DSTRepresenting the effective aperture of the diaphragm.
Satisfying the above conditional expression (12), the aperture of the front end of the imaging lens can be reduced, the volume of the lens can be reduced, the head of the lens can extend forwards, and the angle of view can be prevented from being blocked by other parts of the camera.
In some embodiments, the optical imaging lens satisfies: the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are all glass lenses.
In some embodiments, the optical imaging lens satisfies: the second lens and the seventh lens are glass aspheric lenses, and the first lens, the third lens, the fourth lens, the fifth lens and the sixth lens are glass spherical lenses.
The optical imaging lens has the advantages of ensuring the performance of large aperture, small distortion and high pixel, and improving the imaging capability of a long-range object.
The surface shape of the aspheric surface of the optical imaging lens in the embodiments of the invention satisfies the following equation:
wherein z represents the distance in the optical axis direction from the curved surface vertex, c represents the curvature of the curved surface vertex, K represents the conic coefficient, h represents the distance from the optical axis to the curved surface, and B, C, D, E and F represent the fourth, sixth, eighth, tenth and twelfth order curved surface coefficients, respectively.
In the following embodiments, the thickness, the curvature radius, and the material selection of each lens in the optical imaging lens are different, and specific differences can be referred to in the parameter tables of the embodiments.
First embodiment
Referring to fig. 1, a schematic structural diagram of an optical imaging lens 100 according to a first embodiment of the present invention is shown, where the optical imaging lens 100 sequentially includes, from an object side to an image plane along an optical axis: a first lens L1, a second lens L2, a stop ST, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and a filter G1. The first lens L1 and the second lens L2 before the stop ST form a first group Q1, the third lens L3 after the stop ST form a second group Q2, and the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7 form a third group Q3.
The first lens L1 has negative power, the object-side surface S1 of the first lens is concave, the image-side surface S2 of the first lens is nearly flat, and the first lens L1 is a glass spherical lens.
The second lens L2 has positive refractive power, the object-side surface S3 of the second lens is convex, the image-side surface S4 of the second lens is concave, and the second lens L2 is a glass aspheric lens.
The third lens L3 has positive power, and the object-side surface S5 and the image-side surface S6 of the third lens are both convex surfaces, and the third lens L3 is a glass spherical lens.
The fourth lens L4 has positive optical power, and both the object-side surface S7 and the image-side surface S8 of the fourth lens are convex.
The fifth lens L5 has a negative power, the object-side surface S8 and the image-side surface S9 of the fifth lens are both concave, and the fourth lens L4 and the fifth lens L5 are cemented into a cemented body and are both glass spherical lenses.
The sixth lens L6 has positive optical power, and the object-side surface S10 and the image-side surface S11 of the sixth lens are both convex surfaces, and the sixth lens L6 is a glass spherical lens.
The seventh lens L7 has negative power, and the object-side surface S12 and the image-side surface S13 of the seventh lens are both concave, and the seventh lens L7 is a glass aspherical lens.
The stop ST is provided between the second lens L2 and the third lens L3.
The relevant parameters of each lens in the optical imaging lens 100 provided in the first embodiment of the present invention are shown in table 1-1.
The aspherical parameters of each lens of this example are shown in tables 1 to 2.
In the present embodiment, the distortion curve and the axial chromatic aberration curve of the optical imaging lens 100 are shown in fig. 2 and 3, respectively. As can be seen from fig. 2, the f- θ distortion of the imaging system in this embodiment is within about 0.5% in the full field of view, which indicates that the optical imaging lens 100 has almost no image plane curvature in the working field of view, indicating that the imaging lens has high resolution. As can be seen from fig. 3, in the present embodiment, the maximum axial chromatic aberration of a single wavelength of the optical imaging lens 100 does not exceed 0.025mm, and the difference between two different wavelengths does not exceed 0.03mm, which indicates that the axial chromatic aberration of the optical imaging lens 100 at the pupil edge position is well corrected.
Second embodiment
Referring to fig. 4, a structure diagram of an optical imaging lens 200 according to the present embodiment is shown. The optical imaging lens 200 in the present embodiment is substantially the same as the optical imaging lens 100 in the first embodiment, except that the stop ST of the optical imaging lens 200 in the present embodiment is disposed between the first lens L1 and the second lens L2, the first lens L1 forms the first group Q1, the second lens L2 and the third lens L3 form the second group Q2, the image-side surface S2 of the first lens is a convex surface, the image-side surface S11 of the sixth lens L6 is a concave surface, and the curvature radii and material choices of the lenses are different, and the parameters related to each lens are shown in table 2-1.
The aspherical surface parameters of each lens of this example are shown in Table 2-2.
In the present embodiment, graphs of distortion and axial chromatic aberration of the optical imaging lens 200 are shown in fig. 5 and 6, respectively. As can be seen from fig. 5, the f- θ distortion of the imaging system of the present embodiment in the full field angle is within about 0.3%, which indicates that the optical imaging lens 200 has high resolution. As can be seen from fig. 6, the maximum axial chromatic aberration of a single wavelength of the imaging lens of this embodiment does not exceed 0.015mm, and the difference between two different wavelengths does not exceed 0.02mm, which indicates that the axial chromatic aberration of the optical imaging lens 200 at the pupil edge position is well corrected.
Third embodiment
Referring to fig. 7, a structure diagram of an optical lens 300 according to the present embodiment is shown. The optical lens 300 in the present embodiment is substantially the same as the optical lens 100 in the first embodiment, except that the stop ST of the optical lens 300 in the present embodiment is disposed between the first lens L1 and the second lens L2, the first lens L1 forms the first group Q1, the second lens L2 and the third lens L3 form the second group Q2, the image-side surface S2 of the first lens is a concave surface, and the curvature radius and material selection of each lens are different, and specific relevant parameters of each lens are shown in table 3-1.
The aspherical surface parameters of each lens of this example are shown in Table 3-2.
In the present embodiment, the distortion and the axial chromatic aberration are shown in fig. 8 and 9, respectively. As can be seen from fig. 8, the f-theta distortion of the imaging system of the present embodiment is within about 1.5% in the full field of view, which indicates that the optical imaging lens 300 has high resolution. As can be seen from fig. 9, the maximum axial chromatic aberration of a single wavelength of the imaging lens of the present embodiment does not exceed 0.025mm, and the difference between two different wavelengths does not exceed 0.025mm, which indicates that the axial chromatic aberration of the optical imaging lens 300 at the pupil edge position is well corrected.
Fourth embodiment
Referring to fig. 10, a structure diagram of an optical lens 400 according to the present embodiment is shown. The optical lens 400 of the present embodiment is substantially the same as the optical lens 100 of the first embodiment, except that the stop ST of the optical lens 400 of the present embodiment is disposed between the first lens L1 and the second lens L2, the first lens L1 forms the first group Q1, the second lens L2 and the third lens L3 form the second group Q2, the image-side surface S2 of the first lens is concave, the image-side surface S11 of the sixth lens L6 is concave, and the curvature radius and material selection of each lens are different, and specific parameters related to each lens are shown in table 4-1.
The aspherical surface parameters of each lens of this example are shown in Table 4-2.
In the present embodiment, the distortion and the axial chromatic aberration are shown in fig. 11 and 12, respectively. As can be seen from fig. 11, the f- θ distortion of the imaging system of the present embodiment in the full field of view is within about 0.5%, which indicates that the optical imaging lens 400 has high resolution. As can be seen from fig. 12, the maximum axial chromatic aberration of a single wavelength of the imaging lens of this embodiment does not exceed 0.025mm, and the difference between two different wavelengths does not exceed 0.025mm, which indicates that the axial chromatic aberration of the optical imaging lens 400 at the pupil edge position is well corrected.
Fifth embodiment
Referring to fig. 13, a structure diagram of an optical lens 500 according to the present embodiment is shown. The optical lens 500 of the present embodiment is substantially the same as the optical lens 100 of the first embodiment, except that the stop ST of the optical lens 500 of the present embodiment is disposed between the first lens L1 and the second lens L2, the first lens L1 forms the first group Q1, the second lens L2 and the third lens L3 form the second group Q2, the image-side surface S2 of the first lens is concave, the image-side surface S11 of the sixth lens L6 is concave, and the curvature radius and material selection of each lens are different, and specific parameters related to each lens are shown in table 5-1.
The aspherical surface parameters of each lens of this example are shown in Table 5-2.
In the present embodiment, the distortion and the axial chromatic aberration are shown in fig. 14 and 15, respectively. It can be seen from fig. 14 that the f-theta distortion of the imaging system of the present embodiment is within about-0.3% in the full field of view, which indicates that the optical imaging lens 500 has high resolution. As can be seen from fig. 15, the maximum axial chromatic aberration of a single wavelength of the imaging lens of this embodiment does not exceed 0.025mm, and the difference between two different wavelengths does not exceed 0.025mm, which indicates that the axial chromatic aberration of the optical imaging lens 500 at the pupil edge position is well corrected.
Table 6 shows 5 embodiments described above and their corresponding optical characteristics, including the field angle 2 θ, F # and total optical length TTL, and the values corresponding to each of the foregoing conditional expressions.
Further, the optical imaging lens provided by the embodiment of the invention can effectively correct the problems of optical back focus offset and image force reduction caused by temperature change. Taking the optical imaging lens 100 provided in the first embodiment as an example, as shown in fig. 16, 17, and 18, the defocus curves of the central field of view of the optical imaging lens 100 provided in the first embodiment of the present invention at normal temperature of 20 ℃, high temperature of 125 ℃, and low temperature of-40 ℃ can be seen from the following figures: based on the normal temperature of 20 ℃, when the optical imaging lens 100 is at the high temperature of 125 ℃, the back focus offset of the imaging system is about +2.0 μm, and the MTF reduction is about less than 3.5%; at low temperatures of-40 ℃, the back focus offset of the imaging system is about-1.5 μm and the MTF drop is less than about 3.0%. The back focus offset and the MTF drop of the optical imaging lens provided in other embodiments are also small under high and low temperature conditions, so that the back focus offset brought by the temperature can be well corrected by the optical imaging lens, and the MTF drop is small, thereby effectively ensuring the imaging quality of the lens under high and low temperature environments and greatly improving the thermal stability of the lens.
In summary, in the optical imaging lens provided by the invention, the first group Q1 has negative focal power, so that the aperture of the front end of the lens can be effectively reduced, the pupil radius can be enlarged, and the large-aperture imaging effect of the imaging system can be realized; by controlling the curvature radius of the object side surface of the first lens L1, the relative illumination of the imaging lens can be effectively improved; the second lens L2 is an aspheric lens mainly used for correcting distortion; the third lens L3 and the fourth lens L4 are both lenses with positive focal power, and lenses with specific temperature refractive index coefficients are selected and matched with the focal lengths of the third lens L3 and the fourth lens L4, so that the effect of effectively compensating thermal drift can be achieved; the third lens L3 can effectively reduce the emergent angle of the emergent ray, so that the tolerance sensitivity of the rear lens can be reduced; the fourth lens L4 and the fifth lens L5 form a bonded body, and the difference value of the abbe numbers Vd of the positive lens and the negative lens is more than 40, so that chromatic aberration can be effectively corrected; the sixth lens L6 and the seventh lens L7 are matched with each other, so that the field curvature can be effectively corrected; the seventh lens L7 is an aspheric lens, and can play a role in eliminating aberration and controlling the emergent angle of the chief ray, thereby effectively improving the resolving power of the imaging system and enabling the imaging system to meet higher pixel requirements. Each lens is a glass lens, so that the lens has better thermal stability and mechanical strength, and is beneficial to working in an extreme environment. Each lens is a glass lens, so that the lens has better thermal stability and mechanical strength, and is beneficial to working in an extreme environment.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.